From e8223c761516faf767079fab2aabbfd2e01a7901 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jo=C3=A3o=20Magalh=C3=A3es?= <joamag@gmail.com>
Date: Fri, 1 Jul 2022 11:14:39 +0100
Subject: [PATCH] feat: initial implementation of draw line
---
src/ppu.rs | 67 +++++++++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 61 insertions(+), 6 deletions(-)
diff --git a/src/ppu.rs b/src/ppu.rs
index f50b080d..5c3193c1 100644
--- a/src/ppu.rs
+++ b/src/ppu.rs
@@ -17,7 +17,7 @@ pub const SCREEN_HEIGHT: usize = 154;
/// all of the logic behind the graphics processing and presentation.
/// Should store both the VRAM and HRAM together with the internal
/// graphic related registers.
-/// Outputs the screen as a monochromatic 8 bit frame buffer.
+/// Outputs the screen as a RGBA 8 bit frame buffer.
///
/// # Basic usage
/// ```rust
@@ -25,9 +25,9 @@ pub const SCREEN_HEIGHT: usize = 154;
/// ppu.tick();
/// ```
pub struct Ppu {
- /// The 8 bit based monochromatic frame buffer with the
+ /// The 8 bit based RGBA frame buffer with the
/// processed set of pixels ready to be displayed on screen.
- pub frame_buffer: [u8; SCREEN_WIDTH * SCREEN_HEIGHT],
+ pub frame_buffer: [u8; SCREEN_WIDTH * SCREEN_HEIGHT * RGBA_SIZE],
/// Video dedicated memory (VRAM) where both the tiles and
/// the sprites are going to be stored.
pub vram: [u8; VRAM_SIZE],
@@ -69,7 +69,7 @@ pub enum PpuMode {
impl Ppu {
pub fn new() -> Ppu {
Ppu {
- frame_buffer: [0u8; SCREEN_WIDTH * SCREEN_HEIGHT],
+ frame_buffer: [0u8; SCREEN_WIDTH * SCREEN_HEIGHT * RGBA_SIZE],
vram: [0u8; VRAM_SIZE],
hram: [0u8; HRAM_SIZE],
tiles: [[[0u8; 8]; 8]; TILE_COUNT],
@@ -203,7 +203,62 @@ impl Ppu {
}
}
- fn render_line(&self) {
- //@todo implement the rendering of a line
+ fn render_line(&mut self) {
+ let mut map_offset: usize = if self.bg_map { 0x1c00 } else { 0x1800 };
+ map_offset += (((self.line + self.scy) & 0xff) >> 3) as usize;
+
+ // calculates the sprite line offset by using the SCX register
+ // shifted by 3 meaning as the tiles are 8x8
+ let mut line_offset: usize = (self.scx >> 3) as usize;
+
+ let y = ((self.scy + self.line) & 0x07) as usize;
+ let mut x = (self.scx & 0x07) as usize;
+
+ let mut frame_offset = self.line as usize * SCREEN_WIDTH * RGBA_SIZE;
+
+ let mut tile_index = self.vram[map_offset + line_offset] as usize;
+
+ // if the tile data set in use is #1, the
+ // indices are signed, calculates a real tile offset
+ if self.bg_tile && tile_index < 128 {
+ tile_index += 256;
+ }
+
+ for _index in 0..SCREEN_WIDTH {
+ // in case the end of tile width has been reached then
+ // a new tile must be retrieved for plotting
+ if x == 8 {
+ // resets the tile X position to the base value
+ // as a new tile is going to be drawn
+ x = 0;
+
+ // calculates the new line tile offset making sure that
+ // the maximum of 32 is not overflown
+ line_offset = (line_offset + 1) & 31;
+
+ // calculates the tile index nad makes sure the value
+ // takes into consideration the bg tile value
+ tile_index = self.vram[map_offset + line_offset] as usize;
+ if self.bg_tile && tile_index < 128 {
+ tile_index += 256;
+ }
+ }
+
+ // obtains the current pixel data from the tile and
+ // re-maps it according to the current palette
+ let pixel = self.tiles[tile_index][y][x];
+ let color = self.palette[pixel as usize];
+
+ // set the color pixel in the frame buffer
+ self.frame_buffer[frame_offset] = color[0];
+ self.frame_buffer[frame_offset + 1] = color[1];
+ self.frame_buffer[frame_offset + 2] = color[2];
+ self.frame_buffer[frame_offset + 3] = color[3];
+
+ frame_offset += RGBA_SIZE;
+
+ // increments the current tile X position in drawing
+ x += 1;
+ }
}
}
--
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